Process for the vulcanization of caoutchouc



Watented Dec. 15, 1925.

UNITED STATES PATENT OFFICE.

HERMANN OEI'IME, OF KALK, NEAR COLOGNE, GERMANY, ASSIGNOR TO CHEMISCHE FABRIK KALK GES. MIT BESCHRKNKTER HAFTU'NG, 0F COLOGNE-ON-TI'IE-RHINE,

GERMANY.

PROCESS FOR THE VULCANIZATION OF CAOUTCHOUC.

No Drawing.

To all whom it may concern:

Be it known that I. HERMANN' OnrrMn, citizen of the German Republic, residing at Kalk, near Cologneonthe-Rhine, Germany, have invented certain new and useful Improvements in a Process for the vulcanization of Caoutchouc, of which the following is a specification.

It is well known to employ metallic oxides and preferably zinc oxide with or without the addition of organic accelerators for the combination of sulphur with the caoutchouo substance.

The different kinds of zinc oxide applied in the art of caoutchouc vulcanization are made by the oxidation of zinc vapours at a high temperature with air or steam. I have found that zinc hydroxide and the oxyhydrates of zinc are more effective and far superior to the zinc oxide made by a pyrog enous method as regards the-yulcanization of caoutchouc.

Zinc hydroxide is usually made by pre cipitating zinc salts by bases; There are also other methods of preparing Zinc hydroxide and oxyhrates, for instance, by the decomposition of zinc double salts by bases. All those processes are carried out in the presence of water at common or elevated temperatures, anyhow at far lower temperatures than those employed in the pyrogenous preparation of zinc oxide.

Experiments have shown, that I can prepare by a wet method either pure zinc hy droxide (Zn(OII) or the so-callcd oxyhydrates of zinc of a variable composition:

The percentage of ZnO varies in those compounds from 97.4 to 71%.

()n the other hand I can prepare zinc hydroxide (Zn(OH) by drying different hydratic compounds of zinc oxide. It is also possible to hydrate zinc oxide made by a pyrogenous method, the product obtained containing variable quantities of constitutional water.

Application filed July 13, 1925.

chemical Serial No. 43,402.

I have now found, that nine hydroxide or the oxyhydrates of zinc, prepared by a wet method have a considerably greater power of promoting the combination of sulphur with the caoutchouc substance than the other kinds of zinc oxides made by a pyrogenous method.

Comparative experiments have shown that in the same kinds of caoutchouo mixtures the application of zinc hydroxide or zinc oxyhydrates instead of zinc oxide have the surprisingeitect, that the complete vulcanization of caoutchouc is effected in less than half the time or the quantity of zinc oxyhydrate can be reduce-d to one hali of the quantity of zinc oxide with the same result. Furthermore the temperature of vulcanization can also be considerably reduced, zinc hydroxide exhibiting a far greater chemical activity than zinc oxide. The strength of caoutchouc mixtures is increased by the ap plication of zinc hydroxide in the vulcanization.

I am aware of Pearson having proposed to employ zinc oxide prepared by a wet process for coloring caoutchouc. Pearson describes two methods of preparing zinc oxide, viz a dry process consisting in the oxidation with air or a wet process consisting in the oxidation with steam. Both methods are, however, pyrogenous methods, the oxidation of zinc by air or steam proceeding at a red heat only. The zinc hydroxide and the oxyhydrates of zinc are not suitable for coloring caontchouc possessing practically no power of colorization.

lVhat I claim is:

1. A process for the wilcanization o't (.ilOUlZCllOllC consisting in using zinc hyl1OXI(l"1EO1' the cmnbination'ot sulphur with. tho caoutchouc substance.

52. A process tor the vulcanization ot caout-chouc consisting in using oxyhydrates of zinc for the combination of sulphur with the caoutchouc substance.

In testimony whereof I aflix my signature.

HERMANN OEHME. 

